1. Field of the Invention
The present invention relates to a temperature detection circuit based on temperature characteristics of a semiconductor circuit.
2. Description of the Related Art
FIG. 5 is a schematic diagram showing a normal temperature detection circuit (see JP 2001-165783 A).
The temperature detection circuit includes a temperature sensor circuit 200, a reference voltage circuit 300, a comparator 400, a positive power supply terminal 500, a negative power supply terminal 600, and an output terminal 700. The temperature sensor circuit 200 includes a first terminal, a second terminal, and a third terminal and has a characteristic of reducing an output voltage with an increase in temperature. The first terminal is connected with the positive power supply terminal 500. The second terminal is connected with the negative power supply terminal 600. The third terminal is connected as an output terminal of the temperature sensor circuit 200 with a positive input terminal (+) of the comparator 400. The reference voltage circuit 300 includes a cathode connected with the negative power supply terminal 600 and an anode connected with a negative input terminal (−) of the comparator 400 and generates a reference voltage which is equal to the output voltage of the temperature sensor circuit 200 at a predetermined temperature. The comparator 400 includes a first terminal connected with the positive power supply terminal 500, a second terminal connected with the negative power supply terminal 600, and a third terminal (output terminal) connected with the output terminal 700. The comparator 400 compares the output voltage of the temperature sensor circuit 200 with the reference voltage of the reference voltage circuit 300 to generate a temperature detection signal (negative power supply potential) or a temperature non-detection signal (positive power supply potential).
The operation of the temperature detection circuit shown in FIG. 5 will be described.
When a temperature is lower than the predetermined temperature, the output voltage of the temperature sensor circuit 200 is larger than the reference voltage, so the comparator 400 generates the temperature non-detection signal. On the other hand, when the temperature is equal to or higher than the predetermined temperature, the output voltage of the temperature sensor circuit 200 is equal to or smaller than the reference voltage, so the comparator 400 generates the temperature detection signal. Therefore, the output logic switching operation is performed based on whether or not the temperature is equal to or higher than the predetermined temperature, with the result that the predetermined temperature can be detected.
However, the temperature detection circuit described above may cause the following erroneous operation. Immediately after the activation of the power supply, while the output voltage of the temperature sensor circuit 200 and the reference voltage of the reference voltage circuit 300 are insufficient, the temperature detection circuit generates the temperature detection signal without depending on the temperature because of a relationship between the rising speed of the output voltage of the temperature sensor circuit 200 and the rising rate of the reference voltage of the reference voltage circuit 300.